libdwfl: Introduce dwfl_module_getsym_info and dwfl_module_addrinfo.

libdwfl: Introduce dwfl_module_getsym_info and dwfl_module_addrinfo.

Some arches like ppc64 use function descriptor values instead of function
addresses causing matching of names and addresses to fail when using
dwfl_module_getsym or dwfl_module_addrsym.

Add ebl hook to resolve any function descriptor values found in non-ET_REL
modules.

The new function dwfl_module_getsym_info doesn't adjust the symbol value
in any way, but returns the adjusted and/or resolved address associated
with the symbol separately. The new function dwfl_module_addrinfo resolves
against both the address associated with the symbol (which could be the
function entry address) value and the adjusted st_value. So that it is
easy to resolve and match either function descriptors and/or function
entry addresses.

Since these new functions also return more information they replace the
dwfl_module_getsym_elf and dwfl_module_addrsym_elf functions that never
made it into a released elfutils version.

addr2line and readelf now use the new functions when looking up functions
names. addr2line will now also display the section the address was found
in when given -x.

Extra testcases were added for both addr2line and the dwflsyms testscase.

Signed-off-by: Mark Wielaard <mjw@redhat.com>